Circuit arrangement for thermionic receivers



April 1934- A. ARZMAIER ET AL 1,954,782

CIRCUIT ARRANGEMENT FOR THERMIONIC RECEIVERS Filed Feb. 27, 1929 4 Lawn]Patented Apr. 17, 1934 UNITED STATES PATENT OFFICE CIRCUIT ARRANGEMENTFOR THERMIONIC RECEIVERS Application February 27, 1929, Serial No.343,154 In Germany January 20, 1928 2 Claims.

This invention relates to electric relay circuits and provides animproved method of supplying energy thereto.

It is known in connection with the operation of apparatus comprisingthermionic triodes that, for the purpose of saving the grid battery, thegrid biasing potential may be taken off at separate auxiliaryresistances in the filament and plate leads. In the case ofbattery-eliminator sets this would involve the drawback that the directcurrent potential thus furnished depends upon the load.

The object of this invention is to overcome the above difiiculty. Thisis attained according to the present invention by the use of a tubecircuit arrangement, especially adapted to batteryeliminator sets, inwhich the grid biasing potential is derived from the direct currentresistance of the choke-coils provided for the purpose of smoothing thefeed current. The direct current potential obtainable at these chokecoils, provided the coils are economically designed, is of the order ofmagnitude of the requisite grid biasing potential. In order that thegrid biasing potential thus furnished may be negative in relation to thefilament, it is necessary to include the choke-coils in the negativebranch of the filter circuit. It is also recommendable to provide thecoils with taps in order that grid biasing potentials of differentvalues may be available.

One embodiment of the idea underlying the invention is illustrated byway of example in the single figure of the drawing. The drawing illus-vtrates a two-stage tube amplifier comprising tubes T1 and 12, inputtransformer t1 and output transformer t2. Filament and plate current issupplied to the set at points and it being immaterial whether a directcurrent supply network of fluctuating amplitude is connected across thesaid terminals, or the output circuit of a rectifier connected with analternating current source.

The smoothing means for the feed current ordinarily consist of two coilsd1, d2, which are included in the negative wire, and of condenser 01 andc2 shunted across them. Connected with the said smoothing elements is aresistance 10 arranged potentiometer-fashion, and at the said resistancep are taken off the filament potential and the two plate potentials.

Now, according to the present invention, each of the grids is unitedwith a point or tap of the two choke-coils d1 d2; to be more precise,the grid of tube T1 is associated with coil d2, and the grid of tube T2with the coil dl. In this manner, the grid of the end or power tube r2receives a higher negative bias than the grid of tube r1. Inasmuch as atthe tapping points, the direct current potential has usually superposedon it fluctuating components means in the grid leads in the form ofcondensers c3 and 04, respectively, and of resistances wl and w2,respectively, are provided though in lieu of the resistances alsochoke-coils could be provided for filtering out or by-passing thesecomponents. Since inside the range of negative grid potential no currenthas to be furnished-these smoothing means can be chosen very ample, andthis insures a so much greater filtering effect.

The drop of potential at the choke-coils d1 d2 which should approximatethe maximum necessary grid biasing potential is dependent on the load ofthe outfit. Since the latter is not constant, it follows that the directcurrent potential fall across the choke-coil would vary in anundesirable manner during operation. In order to prevent this action itis of advantage to provide the apparatus with an additional constantload resistance. If the latter is, say, of the order of magnitude of thelowest useful load, then the mean feed current will be about doubled;hence, to insure the same voltage fall across the choke, coils d1 d2only one-half the ohmic resistance or the output, the furnished directcurrent potential, especially the drop of potential across thechoke-coil, is less dependent upon the useful load of the output, Thisalso dispenses with the necessity of subdividing the resistance value orthe choke-coil unduly. The supplementary or auxiliary load resistancemay advantageously consist of the potentiometer proper We claim:

1. In a power supply system to be used with amplifying apparatusincluding a thermionic tube having anode, cathode and controlelectrodes, a source of pulsating direct current, a current smoothingfilter having output terminals, and input terminals connected to saidsource, a potential divider connected across said output terminals, anda filter impedance connected between one of said input terminals and oneof said output terminals, means arranged to provide a connection betweensaid last named output terminal and the cathode of said tube, meanscomprising a direct current connection between an intermediate portionof said filter impedance and the grid electrode for deriving from thedrop across at least a portion of the filter impedance a biasingpotential for said control electrode and an alternating currentconnection between the grid electrode and a point of the circuit betweenthe last named input and output terminals of different potential thanthe point of the impedance connectedto the grid.

2. In a power supply system to be used with amplifying apparatusincluding a thermionic tube having anode, cathode and controlelectrodes, a source of pulsating direct current, a current smoothingfilter having output terminals, and input terminals connected to saidsource, a, potential divider connected across said output terminals anda filter impedance connected between one of said input terminals and oneof said output terminals, said filter impedance being in at least twosections, a capacity connected between an intermediate point of saidimpedance and said other output terminal, means arranged to provide aconnection between said cathode and said potential divider whereby apredetermined average potential is applied to the cathode, meansarranged to provide a connection between said anode and a point of thepotential divider of higher potential than the average potential appliedto the cathode, means including at least a portion of said filterimpedance for providing a direct current connection between the gridelectrode and the cathode of said thermionic device whereby the grid ismaintained at a negative potential with respect to the cathode averagepotential, and means for providing an alternating current path between apoint of said potential divider of lower potential than the said cathodeaverage potential than the derived grid potential.

ALFONS ARZMAIER. ANDREAS JAUMANN.

